Actuation levers that include a lever and a knob secured thereto are well known in the art. Many manufacturers or designers of knobs/actuation lever assemblies, typically require that the knob installation force (i.e. the force required to seat the knob onto the lever) be small enough to manually install a knob without the aid of a force multiplier tool (such as a press, or the like). Similarly, the knob removal force (the force required to separate a knob from its associated actuation lever), is typically required to be large enough to prevent inadvertent removal of the knob during use. Forty Newtons of force or greater is a typical removal force value.
One means of securing a knob to an associated lever includes the use of adhesives to chemically bond the knob to its mating actuation lever. The pre-cured properties of most adhesives permit the knob to be installed onto its associated actuation lever with minimum force. Moreover, the retaining force of cured adhesive readily satisfies the typical removal force requirements. However, application of an adhesive can be costly, especially when the dispensing equipment and labor are considered. Further, the adhesive application process is vulnerable to operator errors (e.g. dispensing too much, or not enough, adhesive). In addition to these drawbacks, the use of an adhesive does not allow the knob to be separated from its associated actuation lever for the purpose of servicing either the knob or the lever, or the component associated with the actuation lever.
Another well-known means of securing a knob to an associated actuation lever includes the use of a mechanical interference fit between the knob and the lever. In this design approach, one end of the lever is typically slightly larger in geometry than the geometry of an associated knob cavity into which the lever is inserted. This relative sizing of the knob cavity and the actuation lever creates frictional interference between the surfaces of the two mating parts. While the use of an interference fit to secure a knob to an actuating lever overcomes the shortcomings of using an adhesive, it does not readily satisfy the above-specified installation and removal force requirements simultaneously. In other words, there are many interference fits that readily meet the specified maximum value but necessitate the use of a force multiplier tool for installation. Likewise, knob and mating actuating levers can be readily designed to meet the minimum installation force but in turn fail to meet the force removal requirement.